1. Field of the Invention
The present invention is directed to lens design and, more particularly, to an apparatus, system and method for predictive modeling to design, evaluate and optimize ophthalmic lenses.
2. Description of the Background
Visual acuity is the clarity of vision, and more specifically is the spatial resolving power of a visual system. Visual acuity is thus the spatial level of detail that can be resolved by the visual system, and may be limited by physiological factors of the patient, such as optical factors within the eye and/or neural factors. Typically, visual acuity is heuristically obtained in an ophthalmic medical practice by presentation of a letter chart to the patient. Visual acuity may be calculated in accordance with the spatial frequency at which the eye's modulation transfer function (MTF) intersects with its neural threshold function (NTF).
The optical transfer function (OTF) describes the spatial variation in a optical system as a function of spatial frequency. The OTF may account for aberration in the optical system, and has a magnitude of the MTF and a phase defined by the phase transfer function (PTF).
An ophthalmic lens may be used to correct aberrations of the eye, as defined using the OTF, for example. An ophthalmic lens may be, for example, an intraocular lens (IOL) that may be surgically implanted, such as a spheric, aspheric, diffractive, refractive, accommodating or injectable IOL, an optical inlay or overlay, or contact lenses or glasses, for example. An IOL is typically implanted to correct medical conditions, such as cataracts and/or presbyopia, for example.
On an individual basis, the modeling of the visual acuity (VA) of ophthalmic lenses using the intersection of the MTF and the NTF has not proven highly accurate when compared with clinical data. Alternative methods of preclinically testing ophthalmic lenses, such as wavefront aberration techniques, have similarly not comported well with clinical data. Further, MTF, wavefront aberration, and other modeling tests have been generally applied to only specific vision conditions, and hence offer only limited predictability of VA and other vision factors, such as contrast sensitivity.
Forty-six (46) physiological eye models for a population of eyes of particular conditions and having particular characteristics have recently been produced by Piers, et al. (See P. A. Piers, H. A. Weeber, P. Artal, and S. Norrby, “Theoretical comparison of aberration correcting customized and aspheric intraocular lenses,” J Refract Surg 23(4), 374-384 (2007), incorporated herein by reference as if set forth in the entirety). The Piers models provide clinically-based models of the eye, and encompass a representative model of the clinical population. The representative models include the aberrations that may be presented in the eye, which may additionally indicate the characteristics of the eye, such as the optical length of the eye, the corneal curvature, the pupil size, and variations thereof, for example. More specifically, the Piers eye models demonstrate wavefront aberrations that are characteristic for a cataract population, and which have been verified against clinical data for contrast vision.
Although modeling techniques are available, as discussed above, and although the Piers models provide simulated eyes to which modeling techniques may be applied, modeling techniques have not been applied to model eyes in a manner that allows for the evaluation and optimization of clinical implementations of lenses designed using the modeling. More particularly, the available art fails to provide feedback from clinical implementations to evaluate and optimize lens design, and to thereby improve the obtained characteristics of subsequent clinical implementations.
Thus, the need exists for an apparatus, system and method for predictive modeling to design, evaluate and optimize ophthalmic lenses.